The invention relates to a heating device, in particular for a motor vehicle, for generating frictional heat by liquid friction.
A heating device of this general type is disclosed by DE-A 198 27 097, which is commonly assigned with the present application. This known heating device is an auxiliary heater for motor vehicles with consumption-optimized engines, in which, therefore, there is relatively little waste heat available from the engine for heating purposes. In the known design, the heating warmth is generated via liquid friction and is dissipated to the coolant of the engine. A rotor which rotates in a working space of the heating device is driven by the internal combustion engine of the motor vehicle. The rotor, together with a wall of the heating device which is fixed to the housing, forms a working gap which is filled with viscous liquid. The shear friction of the viscous liquid in the working gap generates heat which is dependent on the transmitted torque and the engine speed. To limit the heating output to a defined level, it is provided, in the known device, for the rotor to be arranged axially movably on the drive shaft, so that the working gap can be increased in size, and in this way the heating output can be controlled. The axially movable arrangement of the rotor on the drive shaft, which requires a corresponding linear bearing, entails a structural outlay that increases the production costs of a heating device of this type, which is produced in large series for motor vehicles.